Abstract Conclusions: The limitation in olfactory function in patients with seasonal allergic rhinitis (AR) can be ascribed to an increase in eosinophilic and mast cell activity in the olfactory cleft. Therefore, the decrease in olfactory functions seems to be predominantly caused by the inflammation of the epithelium and not by the obstruction of the nose caused by the inflammation. Objective: Olfactory dysfunction is frequently seen in patients with AR; however, little is known about the underlying pathophysiological mechanisms. Therefore, the aim of the present study was to examine the olfactory function in patients with seasonal or perennial AR, and to correlate the results with data obtained by analysis of nasal secretion and obstruction. Methods: Olfactory function was tested using the Sniffin´Sticks test in patients with seasonal or perennial AR and in a control group. Nasal secretion analysis included eosinophilic cationic protein (ECP) and tryptase testing. Nasal obstruction was evaluated by rhinomanometry. Results: Patients with AR (seasonal and perennial) showed impaired olfactory functions in comparison with the control group. Nasal secretion analysis showed increased values of ECP and tryptase in the seasonal group in comparison with controls. Rhinomanometry showed no differences in nasal flow between the three groups.